diff options
Diffstat (limited to 'recipes-kernel/linux/files/CVE-2016-5696-make-challenge-acks-less-predictable.patch')
-rw-r--r-- | recipes-kernel/linux/files/CVE-2016-5696-make-challenge-acks-less-predictable.patch | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/recipes-kernel/linux/files/CVE-2016-5696-make-challenge-acks-less-predictable.patch b/recipes-kernel/linux/files/CVE-2016-5696-make-challenge-acks-less-predictable.patch new file mode 100644 index 0000000..fe67b3b --- /dev/null +++ b/recipes-kernel/linux/files/CVE-2016-5696-make-challenge-acks-less-predictable.patch | |||
@@ -0,0 +1,88 @@ | |||
1 | From 72c2d3bccaba4a0a4de354f9d2d24eccd05bfccf Mon Sep 17 00:00:00 2001 | ||
2 | From: Eric Dumazet <edumazet@google.com> | ||
3 | Date: Sun, 10 Jul 2016 10:04:02 +0200 | ||
4 | Subject: [PATCH] tcp: make challenge acks less predictable | ||
5 | |||
6 | [ Upstream commit 75ff39ccc1bd5d3c455b6822ab09e533c551f758 ] | ||
7 | |||
8 | Yue Cao claims that current host rate limiting of challenge ACKS | ||
9 | (RFC 5961) could leak enough information to allow a patient attacker | ||
10 | to hijack TCP sessions. He will soon provide details in an academic | ||
11 | paper. | ||
12 | |||
13 | This patch increases the default limit from 100 to 1000, and adds | ||
14 | some randomization so that the attacker can no longer hijack | ||
15 | sessions without spending a considerable amount of probes. | ||
16 | |||
17 | Based on initial analysis and patch from Linus. | ||
18 | |||
19 | Note that we also have per socket rate limiting, so it is tempting | ||
20 | to remove the host limit in the future. | ||
21 | |||
22 | v2: randomize the count of challenge acks per second, not the period. | ||
23 | |||
24 | CVE: CVE-2016-5696 | ||
25 | Upstream-Status: Backport | ||
26 | |||
27 | Fixes: 282f23c6ee34 ("tcp: implement RFC 5961 3.2") | ||
28 | Reported-by: Yue Cao <ycao009@ucr.edu> | ||
29 | Signed-off-by: Eric Dumazet <edumazet@google.com> | ||
30 | Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> | ||
31 | Cc: Yuchung Cheng <ycheng@google.com> | ||
32 | Cc: Neal Cardwell <ncardwell@google.com> | ||
33 | Acked-by: Neal Cardwell <ncardwell@google.com> | ||
34 | Acked-by: Yuchung Cheng <ycheng@google.com> | ||
35 | Signed-off-by: David S. Miller <davem@davemloft.net> | ||
36 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | ||
37 | Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com> | ||
38 | --- | ||
39 | net/ipv4/tcp_input.c | 15 ++++++++++----- | ||
40 | 1 file changed, 10 insertions(+), 5 deletions(-) | ||
41 | |||
42 | diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c | ||
43 | index d4c5115..05f10df 100644 | ||
44 | --- a/net/ipv4/tcp_input.c | ||
45 | +++ b/net/ipv4/tcp_input.c | ||
46 | @@ -89,7 +89,7 @@ int sysctl_tcp_adv_win_scale __read_mostly = 1; | ||
47 | EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); | ||
48 | |||
49 | /* rfc5961 challenge ack rate limiting */ | ||
50 | -int sysctl_tcp_challenge_ack_limit = 100; | ||
51 | +int sysctl_tcp_challenge_ack_limit = 1000; | ||
52 | |||
53 | int sysctl_tcp_stdurg __read_mostly; | ||
54 | int sysctl_tcp_rfc1337 __read_mostly; | ||
55 | @@ -3427,7 +3427,7 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb) | ||
56 | static u32 challenge_timestamp; | ||
57 | static unsigned int challenge_count; | ||
58 | struct tcp_sock *tp = tcp_sk(sk); | ||
59 | - u32 now; | ||
60 | + u32 count, now; | ||
61 | |||
62 | /* First check our per-socket dupack rate limit. */ | ||
63 | if (tcp_oow_rate_limited(sock_net(sk), skb, | ||
64 | @@ -3435,13 +3435,18 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb) | ||
65 | &tp->last_oow_ack_time)) | ||
66 | return; | ||
67 | |||
68 | - /* Then check the check host-wide RFC 5961 rate limit. */ | ||
69 | + /* Then check host-wide RFC 5961 rate limit. */ | ||
70 | now = jiffies / HZ; | ||
71 | if (now != challenge_timestamp) { | ||
72 | + u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1; | ||
73 | + | ||
74 | challenge_timestamp = now; | ||
75 | - challenge_count = 0; | ||
76 | + WRITE_ONCE(challenge_count, half + | ||
77 | + prandom_u32_max(sysctl_tcp_challenge_ack_limit)); | ||
78 | } | ||
79 | - if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { | ||
80 | + count = READ_ONCE(challenge_count); | ||
81 | + if (count > 0) { | ||
82 | + WRITE_ONCE(challenge_count, count - 1); | ||
83 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); | ||
84 | tcp_send_ack(sk); | ||
85 | } | ||
86 | -- | ||
87 | 1.9.1 | ||
88 | |||